Hi, there are various words you have used that have rather less than universal meaning. What i understand from your question is that you are talking about an axial propellor i.e. a rotor that does work on the fluid but is not followed by a stator to recover the dynamic head imparted. If a stator is also present then the machine will look like a single stage compressor. Then there is the term "vortex" you may mean what is the distribution of angular momentum in the flow? This terminology was common in the early days of turbomachinery design. Or you may be refering to the vortices in the flow due to secondary flow; passage vortex, horseshoe vortex or tip leakage vortex, all of these are featured in the literature.

If my assumption of axial propellor is correct and that vortex refers to the exit whirl distribution then the euler work equation Work=Delta (U Vtheta) will determine the whirl velocity at exit. All you need to know is the radius, rotational speed and the specific work.

Hope it helps Martin

Good morning Martin.

As you can notice i am not even basic level about the topic and hydrodynamic is not my field at all. I was trying to mean the vortex due to secondary flow, the vortex created behind the blades.

I just need a basic understanding, as i have found some draws describing "physically" the shape and orientation of turbines a lot, but also of axial impellers which are the ones i am interested in. But as the pictures deal with the blade oriented to push the fluid down, i dont know when the blade pushes up (like the outer blade of the impeller i attached an scheme) how this vortex will looks like, if it will go up or down, i hope you can understand me.

Thanks a lot for your answer!

Good morning Abdul,

the thruth is that i need the flow pattern for some experiments already done so i am not planning to change the impeller but thanks a lot for the advance.

As it told an i dont know so much of hydrodynamics, my work is related with particle deposition, and as the impeller makes impact the particle suspension in some baffles y just wanted to relate the zone of depositions with flow patterns and i was wondering about the direction etc. of the trailing vortex as they are scheme for example here in Figure 4, http://www.thermopedia.com/fr/content/549/ but for my outer blade that is going up, so then i was not sure if the trailing vortex of the back side of each blade will be generated in the down edge of the pitched blade and will exit up or what style will show. I am not sure if you are already answering me with the description of the angle of attack, but i am so lost with terms as pressure zone, suction side..cause i dont know anything about impellers.

Thanks a lot Abdul!

I think the Fig. 4 in the paper is assuming the blade is fixed and let the fluid flow toward the blade. In your simulation, if the fluid is fixed and blade is rotating, you might need to change it by rotating you coordinate system with the same rotation as blade to fix the blade.

How does the blade rotate anyway? Clockwise or Anti-clockwise looking downward for example?

 There is a wall effect as in Fig 1 in the reference. Do you consider that in your simulation?

If the propeller rotate clockwise looking from top to down, the flow to the inner bade looks like --> \ , while it is --> / for the outer blade. The vortex will generate on the back side of blade, so the inner blade vortex rotate clockwise pointing toward the vertical axis (downwash) while the outer blade vortex rotate anti-clockwise pointing away vertical axis (upwash). That's why we see the fluid near the vertical axis flowing downward. 

El vortice tiene por lo regular un comportamiento tipico tal como esta descrito por el modelo de vortice de Rankine, con un nucleo rotacional al centro y un flujo irrotacional en la periferia, esto hace que el flujo axial circule preferentemente de forma anular, dejando al nucleo como si fuera una zona estanca. Si ademas colocamos al vortice en un tubo difusor, al conservar su cantidad de movimiento angular, el flujo tiende a rotar a menor velocidad en la medida que aumentar la seccion del tubo difusor. Tambien si la seccion no cambia la friccion se encarga de disminuir la velocidad angular del vortice. Esto hace que la presión en el nuceo del vortice sea menos negativa que la que tuvo al inicio. Como resultado se forma un gradiente de presión adverso que se encarga de mover el flujo en direccion opuesta al fujo principal.

Good morning, sorry for not answering faster. Thanks a lot for your answers. The thruth Shiuh-Hwa Shyu is that i have not done the model of the figure i attached, so honestly i am not sure if the impeller rotates or if the fluid does. It is sure that is clockwise rotation, but your answer is really helpful cause you told me that then, the outer blade will generate a vortex in the back side of the blade which will point away up direction in the vertical axis :-)

Thanks to everyone